This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This protocol is part of an investigator initiated IND (74,247) with the FDA for the investigational drug ABT-751. The protocol has been developed by the Therapeutic Advances in Childhood Leukemia (TACL) consortium in which the Operations Center is located at CHLA and the medical director is Dr. Paul Gaynon. TACL s mission is to develop protocols using new drugs in which provide an improvement upon the historical remission rate of 40% for patient treated with multiple relapsed ALL. ABT-751 drug is provided for use in this protocol by Abbott Laboratories. This is a multi-center phase I/II study whose primary objectives are 1) to establish in relapsed pediatric ALL patients a maximum tolerated dose (MTD) of ABT-751 in the context of a re-induction regimen that also includes dexamethasone, PEG-asparaginase, and doxorubicin, and 2) to determine whether there is evidence that ABT-751 will improve re-induction success rate in this context. The study will be performed in two parts. In Part 1, patients will be treated at one of a series of doses of ABT-751 according to a standard dose escalation design in order to establish the MTD. In Part 2, the 6 patients treated at the MTD in Part 1 will serve as the first stage of a multistage Phase II design, which will be used to evaluate the efficacy of this re-induction regimen.